.\" Copyright (c) 1983, 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" %%%LICENSE_START(BSD_4_CLAUSE_UCB)
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\" %%%LICENSE_END
.\"
.\"     @(#)socketpair.2	6.4 (Berkeley) 3/10/91
.\"
.\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>
.\" Modified 1996-10-22 by Eric S. Raymond <esr@thyrsus.com>
.\" Modified 2002-07-22 by Michael Kerrisk <mtk.manpages@gmail.com>
.\" Modified 2004-06-17 by Michael Kerrisk <mtk.manpages@gmail.com>
.\" 2008-10-11, mtk: Add description of SOCK_NONBLOCK and SOCK_CLOEXEC
.\"
.TH SOCKETPAIR 2 2021-03-22 "Linux" "Linux Programmer's Manual"
.SH NAME
socketpair \- create a pair of connected sockets
.SH SYNOPSIS
.nf
.B #include <sys/socket.h>
.PP
.BI "int socketpair(int " domain ", int " type ", int " protocol \
", int " sv [2]);
.fi
.SH DESCRIPTION
The
.BR socketpair ()
call creates an unnamed pair of connected sockets in the specified
.IR domain ,
of the specified
.IR type ,
and using the optionally specified
.IR protocol .
For further details of these arguments, see
.BR socket (2).
.PP
The file descriptors used in referencing the new sockets are returned in
.I sv[0]
and
.IR sv[1] .
The two sockets are indistinguishable.
.SH RETURN VALUE
On success, zero is returned.
On error, \-1 is returned,
.I errno
is set to indicate the error, and
.I sv
is left unchanged
.PP
On Linux (and other systems),
.BR socketpair ()
does not modify
.I sv
on failure.
A requirement standardizing this behavior was added in POSIX.1-2008 TC2.
.\" http://austingroupbugs.net/view.php?id=483
.SH ERRORS
.TP
.B EAFNOSUPPORT
The specified address family is not supported on this machine.
.TP
.B EFAULT
The address
.I sv
does not specify a valid part of the process address space.
.TP
.B EMFILE
The per-process limit on the number of open file descriptors has been reached.
.TP
.B ENFILE
The system-wide limit on the total number of open files has been reached.
.TP
.B EOPNOTSUPP
The specified protocol does not support creation of socket pairs.
.TP
.B EPROTONOSUPPORT
The specified protocol is not supported on this machine.
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008, 4.4BSD.
.BR socketpair ()
first appeared in 4.2BSD.
It is generally portable to/from
non-BSD systems supporting clones of the BSD socket layer (including
System\ V variants).
.SH NOTES
On Linux, the only supported domains for this call are
.B AF_UNIX
(or synonymously,
.BR AF_LOCAL )
and
.B AF_TIPC
.\" commit: 70b03759e9ecfae400605fa34f3d7154cccbbba3
(since Linux 4.12).
.PP
Since Linux 2.6.27,
.BR socketpair ()
supports the
.BR SOCK_NONBLOCK
and
.BR SOCK_CLOEXEC
flags in the
.I type
argument, as described in
.BR socket (2).
.SH SEE ALSO
.BR pipe (2),
.BR read (2),
.BR socket (2),
.BR write (2),
.BR socket (7),
.BR unix (7)
.SH COLOPHON
This page is part of release 5.13 of the Linux
.I man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
\%https://www.kernel.org/doc/man\-pages/.
